Rotary axis module and articulated robot

ABSTRACT

A rotary axis module includes: an input shaft connected to a drive motor; an output shaft, an output shaft flange connected to the output shaft; parallel gears coupled to the output shaft flange; at least two double gears; and a transfer gear that transmits the power of the drive motor to the double gears. The at least two double gears and the transfer gear are disposed so as to surround the output shaft.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 15/626,428, filedJun. 19, 2017, which claims the benefit of priority from Japanese PatentApplication No. 2016-155025, filed on Aug. 5, 2016, the contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a rotary axis module and an articulatedrobot provided with the rotary axis module.

2. Description of the Related Art

A conventional gear reduction mechanism including multiple gears is usedto transmit rotary power to, for example, a robot arm of an industrialrobot from an electric motor. A gear reduction mechanism disclosed inJapanese Unexamined Patent Publication (Kokai) No. 9-119486 includes aninput gear connected to a rotary power source, e.g., an electric motor,an output gear connected to a rotated member, e.g., a robot arm, and anintermediate gear assembly engaged with the input gear and the outputgear. The intermediate gear assembly of Japanese Unexamined PatentPublication (Kokai) No. 9-119486 is mounted on the same mounting surfaceas the rotary power source and the rotated member.

Moreover, Japanese Unexamined Patent Publication (Kokai) No. 2014-612discloses a speed reduction mechanism including multiple double spurgears. The double spur gears are linearly arranged between an input gearand an output gear. Thus, when such a speed reduction mechanism isdisposed on the end of a robot wrist, the wrist end can be reduced insize in the thickness (height) direction and the width direction.

SUMMARY OF THE INVENTION

In Japanese Unexamined Patent Publication (Kokai) No. 2014-612, however,the double spur gears are linearly arranged by an umbilical memberbetween the input gear and the output gear, thereby increasing the sizeof the speed reduction mechanism in the direction of arrangement (armlongitudinal direction).

The present invention has been devised under these circumstances. Anobject of the present invention is to provide a rotary axis module thatcan be reduced in size.

In order to attain the object, a first aspect provides a rotary axismodule including: an input shaft connected to a drive motor; an outputshaft; an output shaft flange connected to the output shaft; parallelgears coupled to the output shaft flange; a reduction-drive outer caserotatably supported by the output shaft flange; a double gear trainincluding at least two double gears disposed in the reduction-driveouter case; and a transfer gear that transmits power of the drive motorto the double gear train, wherein the parallel gear is engaged with apinion of one of the at least two double gears while a gear wheel of theother double gear of the at least two double gears is engaged with thetransfer gear, and the at least two double gears and the transfer gearare disposed in a space between an inner surface of the reduction-driveouter case and the output shaft so as to surround the output shaft.

According to a second aspect, in the first aspect, the at least twodouble gears are each supported by support bearings and a supportmember, and the support member is fixed to a mounting flange where thedrive motor is mounted.

According to a third aspect, in the first or second aspect, the outputshaft has a hollow for passage of an umbilical member.

According to a fourth aspect, in any one of the first to third aspects,the parallel gear is an internal gear.

A fifth aspect, in any one of the first to fourth aspects, furtherincludes bearings whose inner surface sides are coupled to the outputshaft flange, the bearings being angular back-to-back duplex bearings.

According to a sixth aspect, in any one of the second to fifth aspects,at least one of the support members of the double gears is supported byboth of the pinion and the gear wheel.

According to a seventh aspect, in any one of the second to sixthaspects, the support members of the at least two double gears areconnected to each other via a reinforcing member.

According to an eighth aspect, in any one of the second to seventhaspects, at least one of the support bearings of the at least two doublegears includes a needle bearing.

According to a ninth aspect, in any one of the second to eighth aspects,at least one of the support bearings of the at least two double gearsincludes a ball bearing.

According to a tenth aspect, in any one of the first to ninth aspects, areduction ratio between the parallel gear and the pinion of one of thedouble gears is larger than a reduction ratio between the gear wheel ofone of the double gears and the pinion of the other double gear.

According to an eleventh aspect, in any one of the first to tenthaspects, the at least two double gears each include a shaft partextending from an end face of the gear wheel, the shaft part beingsupported so as to support the double gear like a cantilever.

According to a twelfth aspect, in any one of the first to eleventhaspects, an oil seal used in the rotary axis module includes at leastone lip that has a minimum tension without suppressing a sealingfunction.

According to a thirteenth aspect, in any one of the first to twelfthaspects, the drive motor is mounted on a mounting surface of the outputshaft flange such that a rotary axis of the drive motor is in parallelwith the mounting surface.

A fourteenth aspect provides an articulated robot including at least onerotary axis module according to any one of the first to thirteenthaspects.

A detailed description about typical embodiments of the presentinvention shown in the accompanying drawings further clarifies theobject, characteristics, advantages of the present invention and otherobjects, characteristics, and advantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view showing a rotary axis module of the presentinvention;

FIG. 1B is a cross-sectional view taken along line A-A of FIG. 1A;

FIG. 1C is a side view of the rotary axis module shown in FIG. 1A;

FIG. 2 is a partially exploded perspective view showing a rotary axismodule according to a first embodiment of the present invention;

FIG. 3A is a cross-sectional view taken along line B-B of FIG. 1B;

FIG. 3B is a cross-sectional view taken along line C-C of FIG. 1B;

FIG. 4 is a partially transparent end view of the rotary axis moduleshown in FIG. 1A;

FIG. 5 is a cross-sectional view showing a rotary axis module includinga planet gear reduction drive;

FIG. 6 is a partially exploded perspective view showing a rotary axismodule according to a second embodiment of the present invention;

FIG. 7A is a front view of a double gear;

FIG. 7B is a cross-sectional view of the double gear;

FIG. 8A is a first partial perspective view of the rotary axis module;

FIG. 8B is a second partial perspective view of the rotary axis module;

FIG. 8C is a third partial perspective view of the rotary axis module;

FIG. 9A is a partially transparent end view of the rotary axis module;

FIG. 9B is another partially transparent end view of the rotary axismodule;

FIG. 10 is a cross-sectional view of the double gear;

FIG. 11A is a partial cross-sectional view of the rotary axis module;

FIG. 11B is a partially enlarged view showing a part of FIG. 11A;

FIG. 12 is a cross-sectional view showing a rotary axis module accordingto another embodiment of the present invention; and

FIG. 13 shows a robot including the rotary axis module of the presentinvention.

DETAILED DESCRIPTION

Embodiments of the present invention will be described below withreference to the accompanying drawings. In the following drawings, thesame members will be indicated by the same reference symbols. For clearunderstanding, the scales of the drawings are optionally changed.

FIG. 1A is a side view showing a rotary axis module of the presentinvention. FIG. 1B is a cross-sectional view taken along line A-A ofFIG. 1A. FIG. 1C is an end view showing the rotary axis module of FIG.1A.

As illustrated in these drawings, a rotary axis module 10 issubstantially shaped like a cylinder covered with a reduction-driveouter case 13. The rotary axis module 10 may not be cylindrical. Aninput shaft 11 is disposed on one end face of the rotary axis module 10while an output shaft 12 is disposed on the other end face of the rotaryaxis module 10.

The end face near the input shaft 11 serves as a mounting flange 16 onwhich a drive motor 90 is mounted. The drive motor 90 transmits a rotaryforce to the input shaft 11. Moreover, the end face near the outputshaft 12 is configured as an output shaft flange 15 connected to theoutput shaft 12.

FIG. 2 is a partially exploded perspective view showing a rotary axismodule according to a first embodiment of the present invention. FIG. 3Ais a cross-sectional view taken along line B-B of FIG. 1B. FIG. 3B is across-sectional view taken along line C-C of FIG. 1B. As shown in FIGS.2 and 3A, an external gear 17 serving as a parallel gear is coupled tothe output shaft flange 15. The external gear 17 is, for example, a spurgear or a helical gear.

Furthermore, a pinion 21 a of a first double gear 21 is engaged with theexternal gear 17. As shown in FIGS. 2 and 3B, a pinion 22 a of a seconddouble gear 22 is engaged with a gear wheel 21 b of the first doublegear 21. Moreover, a pinion 23 a of a third double gear 23 is engagedwith a gear wheel 22 b of the second double gear 22.

In addition, a pinion 24 a of a fourth double gear 24 is engaged with agear wheel 23 b of the third double gear 23. Finally, a transfer gear 91for transferring the power of the drive motor 90 is engaged with a gearwheel 24 b of the fourth double gear 24. In FIG. 2, the gears areengaged with each other at five points, that is, the first to fourthdouble gears 21 to 24 and the transfer gear 91. Hence, a five-levelspeed reduction mechanism is shown in FIG. 2.

FIG. 4 is a partially transparent end view of the rotary axis moduleshown in FIG. 1A. Referring to FIGS. 1B and 4, a plurality of the doublegears 21 to 24 and the transfer gear 91 are disposed in a space betweenthe inner surface of the reduction-drive outer case 13 and the outputshaft 12 so as to surround the output shaft 12. In other words, in thepresent invention, the double gears 21 to 24 and the transfer gear 91are not linearly arranged. In the present invention, it is understoodthat the double gears 21 to 24 and the transfer gear 91 surround theoutput shaft 12 and thus a rotary axis module 10 can be reduced in size.The number of double gears may be an integer not smaller than 2.

Moreover, the rotary axis module 10 of the present invention onlyincludes the double gears 21 to 24 and the external gear 17. These gearsare parallel gears having high reverse efficiency. Thus, if the rotaryaxis module 10 is applied to a robot, particularly a human friendlyrobot as will be described later, an external force can be transmittedfrom the output arm to the input motor of the robot with higherefficiency.

For example, if a person collides with a robot, the force of collisionis transmitted to an input motor with high sensitivity. The force isused to obtain the contact stop function of a human friendly robot withhigh sensitivity. For the same reason, a readthrough function is easilyobtained that allows an operator to manually teach a teaching positionto a robot.

Furthermore, an external force is easily transmitted to the input unitof the rotary axis module 10 and thus various sensors required for thecontact stop function and the readthrough function may be reduced innumber or may be replaced with inexpensive sensors having lowresolutions. This proves that the rotary axis module 10 can be producedat lower cost than the related art.

As shown in FIG. 1B, the double gears 21 to 24 are not disposed in theright space of the reduction-drive outer case 13. Additional doublegears may be disposed so as to eliminate the right extra space. In thiscase, the total reduction ratio of the rotary axis module 10 can beincreased. Alternatively, the reduction-drive outer case 13 may bepartially recessed to eliminate the extra space. This reduces the weightof the reduction-drive outer case 13 and the amount of lubrication oilcontained in a reduction drive, thereby reducing the weight of theoverall rotary axis module.

Referring to FIG. 2 again, the circumference of the output shaft flange15 is coupled to the inner surface sides of large bearings 18 a and 18 band the reduction-drive outer case 13 is coupled to the outer surfacesides of the large bearings 18 a and 18 b. As described above, theexternal gear 17 is coupled around the center of the output shaft flange15. Thus, the large bearings 18 a and 18 b receive a force applied fromthe outside to the output shaft 12 and a force applied from the pinion21 a of the first double gear 21.

The large bearings 18 a and 18 b are preferably angular back-to-backduplex bearings having relatively large sizes with small friction.Angular back-to-back duplex bearings used as the large bearings 18 a and18 b can simultaneously receive a moment applied to the output shaft 12and a radial load applied to the parallel-axis spur gear 17.Furthermore, this can minimize a reduction in the transmissionefficiency of an external force from the output shaft to the inputshaft. In addition, the angular back-to-back duplex bearings areassembled into the rotary axis module 10 as they are, advantageouslyeliminating the need for a preload adjustment in the manufacturing ofthe rotary axis module 10.

FIG. 5 is a cross-sectional view showing a rotary axis module includinga planet gear reduction drive. The rotary axis module shown in FIG. 5includes a first planet-gear speed reduction mechanism 30 a and a secondplanet-gear speed reduction mechanism 30 b. The planet gear reductionmechanisms 30 a and 30 b respectively include sun gears 31 a and 31 b,internal gears 33 a and 33 b, and planet gears 32 a and 32 b engagedwith the sun gears 31 a and 31 b and the internal gears 33 a and 33 b.

In FIG. 5, the sun gear 31 a of the planet gear reduction mechanism 30 ais combined with the input shaft 11. The output of the planet gearreduction mechanism 30 a is transmitted to the sun gear 31 b of thesecond planet-gear speed reduction mechanism 30 b through a carrier 34.Moreover, a cross roller bearing 35 is disposed between the internalgear 33 b and the output shaft flange 15.

Generally, a single-stage planet gear reduction mechanism can transmit alarge force but cannot obtain a large reduction ratio. Thus, a planetgear reduction mechanism having at least three stages is necessary forobtaining the same reduction ratio as the rotary axis module 10configured as shown in FIG. 2. Consequently, the rotary axis moduleincluding the planet gear reduction mechanism is axially extended. Incontrast, the rotary axis module 10 in FIG. 2 can be axially shorterthan the rotary axis module including the planet gear reductionmechanism.

Furthermore, the planet gears rotate about the sun gear in the planetgear reduction mechanism, leading to great difficulty in backlashadjustment, whereas in the rotary axis module 10 of FIG. 2, a backlashcan be adjusted only by adjusting the position of specific double gears.

For example, only the positions of the first double gear 21, the thirddouble gear 23, and the fourth double gear 24 may be adjusted in FIG. 4.The fourth double gear 24 is adjacent to the drive motor 90 so as toreduce the influence of a backlash according to a total reduction ratiobetween the third double gear 23 and the first double gear 21. Thus, anadjustment of the fourth double gear 24 may be omitted. It is understoodthat the rotary axis module 10 in FIG. 2 remarkably facilitates backlashadjustment.

FIG. 6 is a partially exploded perspective view showing a rotary axismodule according to a second embodiment of the present invention. Asshown in FIG. 6, an internal gear 19 serving as a parallel gear iscoupled to an output shaft flange 15. The internal gear 19 is, forexample, a spur gear or a helical gear. In FIG. 6, a pinion 21 a of afirst double gear 21 is engaged with the internal gear 19 coupled to theoutput shaft flange 15. Other configurations are substantially identicalto the configurations described with reference to FIG. 2 and thus theexplanation thereof is omitted.

When compared with the rotary axis module 10 including the external gear17 shown in FIG. 2, a rotary axis module 10 shown in FIG. 6 can furtherincrease a reduction ratio between the internal gear 19 and the pinion21 a of the first double gear 21.

In FIGS. 2 and 6, a hollow 12 a for passage of linear members, e.g.,driving cables and air tubes is formed at the center of an output shaft12. Thus, when the rotary axis module 10 is mounted in a robot arm,umbilical members can be easily stored in the robot arm so as not to beexposed to the outside.

The hollow 12 a preferably includes a pipe member penetrating the rotaryaxis module 10. In this case, an O-ring is preferably disposed betweenthe pipe member and an output shaft flange 15. In addition, an oil sealand a ball bearing are preferably provided between the pipe member and amounting flange 16. Thus, the pipe member can be supported in a sealedstate.

FIG. 7A is a front view of a double gear. FIG. 7B is a cross-sectionalview of the double gear. In these drawings, for example, a first doublegear 21 is illustrated. However, other double gears 22 to 24 may havesubstantially similar configurations.

As shown in FIGS. 7A and 7B, a gear support part 51 mainly includes abase 5 a, a support member 51 b vertically extending from the base 5 a,and an arm member 51 c that is extended from the base 51 a and isengaged with the distal end of the support member 51 b. The first doublegear 21 is rotatably inserted onto the support member 51 b.

Generally, a falling moment is applied to the support member of a doublegear. A large falling moment is applied to, in particular, the supportmember 51 b of the first double gear 21 engaged with the parallel gear17 of the output shaft 12. In the configuration shown in FIGS. 7A and7B, however, both ends of the double gear 21 are supported and thus thesupport member 51 b can stably support the double gear 21 even if alarge falling moment is applied. This can also increase the reductionratio of the double gear 21.

In this way, both ends of the support member 51 b are supported by thebase 51 a and the arm member 51 c and thus the support member 51 bhardly inclines. As is evident from FIG. 2 and so on, the gear supportpart 51 is stored in the reduction-drive outer case 13 so as not tointerfere with the output shaft flange 15 and the external gear 17 orthe internal gear 19 that is coupled to the output shaft flange 15.Moreover, as shown in FIG. 2 and so on, the base 51 a is mounted on amounting flange 16 of the rotary axis module 10.

As shown in FIG. 7B, a needle bearing 56 is disposed between the firstdouble gear 21 and the support member 51 b. The needle bearing 56 canradially bear a load, thereby reducing the diameter of the pinion 21 aand increasing a reduction ratio per each point of engagement. Thus, thereduction ratio of the double gear can be increased.

When the rotary axis module 10 is swung, a force is applied so as toaxially move the double gear 21 and so on. However, the gear supportpart 51 may be broken by such a force.

In the present invention, as shown in FIG. 7B, a ball bearing 55, forexample, a deep groove ball bearing is disposed on the pinion 21 a ofthe first double gear 21. The ball bearing 55 can bear, for example, athrust load caused by weight applied to the double gear, thereby bearinga force that axially moves the double gear 21. Thus, even when therotary axis module 10 is swung, damage to the gear support part 51 canbe prevented. In this case, a clearance is always formed between theouter cylindrical surface of the ball bearing 55 and the inner matingcylindrical surface of the pinion 21, allowing the ball bearing 55 toreceive only a thrust load without directly receiving a radial loadapplied to the pinion 21 a.

FIGS. 8A to 8C are partial perspective views of the rotary axis module10. In these drawings, the reduction-drive outer case 13, the outputshaft flange 15, the large bearings 18 a and 18 b, the parallel gears 17and 19 and so on are omitted to facilitate understanding.

FIG. 8A corresponds to a part of the rotary axis module 10 shown in FIG.2. In FIG. 8B, the support member 51 b of the first double gear 21 andthe support member 51 b of the second double gear 22 are connected toeach other via a reinforcing member 6 a, e.g., a beam member. In FIG.8C, the arm member 51 c of the first double gear 21 and the supportmember 51 b of the second double gear 22 are connected to each other viaa reinforcing member 61 b.

As described above, the support members 51 b of the two adjacent doublegears are connected to each other via the reinforcing member 61 a. Thiscan further reinforce the support member 51 b of the first double gear21 and the support member 51 b of the second double gear 22. Thereinforcing member 61 a is preferably mounted after the backlashadjustment of the double gears 21 and 22.

Alternatively, another two double gears may be connected to each othervia a reinforcing member or three or more double gears may be connectedto one another via a single reinforcing member, which is notillustrated. Moreover, two double gears that are not adjacent to eachother, for example, the second double gear 22 and the fourth double gear24 may be connected to each other via a reinforcing member within thescope of the present invention.

FIGS. 9A and 9B are partially transparent end view of the rotary axismodule. In FIG. 9A, the parallel gear 17 has a relatively small numberof teeth, whereas the pinion 21 a of the first double gear 21 has arelatively large number of teeth. In FIG. 9B, a parallel gear 17′ has arelatively large number of teeth, whereas the pinion 21 a of the firstdouble gear 21 has a relatively small number of teeth.

In this regard, it is assumed that the total reduction ratio of theconfiguration in FIG. 9A is equal to the total reduction ratio of theconfiguration in FIG. 9B. In FIG. 9A, a small reduction ratio isobtained at the fifth stage, that is, the first double gear 21. Thus, inthe configuration of FIG. 9A, a large reduction ratio is necessarybetween the second double gear 22 and the fourth double gear 24.

Regarding this point, a diameter difference needs to be increasedbetween the pinion and the gear wheel of the double gear of the finalstage in a plurality of successive double gears. This is because areduction ratio cannot be obtained at the double gear of the previousstage of the final stage. Thus, a reduction ratio needs to be obtainedbetween the gear wheel 21 b of the first double gear 21 and the pinion22 a of the second double gear 22 in FIG. 9A. For this reason, in theconfiguration of FIG. 9A, the reduction-drive outer case 13 needs to beincreased in size, thereby upsizing the rotary axis module 10.

In contrast, in the configuration of FIG. 9B, the parallel gear 17′ hasa larger number of teeth than the parallel gear 17. A reduction ratiobetween the parallel gear 17′ and the pinion 21 a of the first doublegear 21 is larger than a reduction ratio between the gear wheel 21 b ofthe first double gear 21 and the pinion 22 a of the second double gear22. In other words, in the configuration of FIG. 9B, the gear wheel 21 bof the first double gear 21 has a relatively small diameter, therebyreducing the size of the reduction-drive outer case 13.

FIG. 10 is a cross-sectional view of the double gear. In FIG. 10, forexample, the second double gear 22 is illustrated. However, other doublegears 21, 23, and 24 may have substantially similar configurations.

In FIG. 10, a shaft part 25 is extended from the center of the outer endface of the gear wheel 22 b so as to stand upright with respect to theouter end face. Moreover, a support base 40 having a recessed part 41 onthe top surface is mounted on the mounting flange 16. As shown in FIG.10, the shaft part 25 of the second double gear 22 is inserted into therecessed part 41 so as to rotate on the top surface of the support base40 through a bearing 45. Thus, in the configuration of FIG. 10, thesecond double gear 22 is supported like a cantilever.

In this configuration, bearings near the pinion 22 a can be eliminatedand thus the pinion 22 a can have a smaller diameter than in theconfiguration of FIG. 7B where the needle bearing 56 is disposed.Furthermore, a reduction ratio per each point of engagement can befurther increased. The bearing 45 that supports the shaft part 25preferably has a relatively large moment capacity. For example, thebearing 45 is preferably an angular back-to-back duplex bearing.

FIG. 11A is a partial cross-sectional view of the rotary axis module.FIG. 11B is a partially enlarged view of FIG. 11A. As shown in FIG. 11B,a seal member is disposed between the reduction-drive outer case 13 andthe output shaft flange 15. The seal member is an oil seal 71 that mayinclude at least one main lip 72. As shown in FIG. 11B, the main lip 72is in contact with the output shaft flange 15 with a small contactsurface.

Generally, the rolling friction of the oil seal may reduce thetransmission efficiency of an external force from the output shaft tothe input shaft. Thus, in the present invention, the main lip 72 is usedthat has a minimum tension without suppressing the sealing function.This can minimize the rolling friction, leading to a minimum frictionloss. Thus, it is understood that the transmission efficiency can befurther increased. Such a low-tension oil seal is desirably applied toall oil seals used in the rotary axis module.

FIG. 12 is a cross-sectional view showing a rotary axis module accordingto another embodiment of the present invention. In FIG. 12, the axis ofa drive motor 90 is perpendicular to the central axis (output axis) of arotary axis module 10. A first bevel gear 91 a is mounted on the outputshaft of the drive motor 90 and is engaged with a second bevel gear 91b. Moreover, the second bevel gear 91 b is engaged with a gear wheel 24b of a fourth double gear 24. In other words, in the configuration ofFIG. 12, the first bevel gear 91 a and the second bevel gear 91 b form atransfer gear 91.

In this case, the drive motor 90 is disposed such that the rotary axisof the drive motor 90 is in parallel with an output shaft flange 15,thereby shortening the rotary axis module 10 in the direction of theoutput shaft. In FIG. 12, the drive motor 90 needs to be disposed nearone end of a hollow 12 a so as to keep the opening of the hollow 12 a.

FIG. 13 shows a robot including the rotary axis module of the presentinvention. The robot 1 in FIG. 13 is a six-axis vertical articulatedrobot including six joint axes J1 to J6. The joint axes are driven bythe rotary axis module 10 or a rotary axis module 10′.

An arm of the robot 1 includes multiple arm parts. The rotary axismodules 10 and 10′ are disposed between the two adjacent arm parts. Therobot 1 shown in FIG. 13 includes the three rotary axis modules 10 andthe three rotary axis modules 10′ smaller than the rotary axis modules10.

The robot 1 includes the rotary axis modules 10 and 10′ and the armparts and thus can be easily reassembled when a user changes the purposeof use. This also advantageously facilitates automatic manufacturing fora manufacturer of the robot 1.

All the axes of the robot may include identical rotary axis modules.Typically, arms are lightweight on the axes of the distal ends of therobot 1 and thus the rotary axis modules 10 do not need to be identicalin the overall robot 1. In the present invention, the three rotary axismodules 10 are disposed on the proximal ends of the robot 1, whereas thethree rotary axis modules 10′ are disposed on the distal ends of therobot 1. In other words, the compact rotary axis modules 10′ are used onthe distal ends of the robot 1.

Thus, the weight of the overall arm and the cost can be reduced ascompared with the use of identical rotary axis modules on all the axes.If the mounting interface of the rotary axis module is shared by all theaxes, the arms are lightweight on the axes of the distal ends of therobot 1, thereby reducing a load applied to a movable member. Thus, thenumber of bolts for fixing the rotary axis modules 10 and 10′ may bereduced.

Effects of Aspects

According to a first aspect, at least two double gears and a transfergear are disposed so as to surround the output shaft, thereby reducingthe size of a rotary axis module. Moreover, the rotary axis module onlyincludes parallel gears having high reverse efficiency, therebyimproving the transmission efficiency of an external force from anoutput arm to an input motor.

According to a second aspect, the double gears can be stably fixed on amounting flange.

According to a third aspect, umbilical members, e.g., driving cables andair tubes can be inserted into a hollow. Thus, when the rotary axismodule is mounted in a robot arm, umbilical members can be easily storedin the robot arm so as not to be exposed to the outside.

According to a fourth aspect, if the parallel gear is an internal gear,a larger reduction ratio can be obtained than an external gear servingas the parallel gear.

According to a fifth aspect, in the case of an angular back-to-backduplex bearing, the bearing can simultaneously receive a moment appliedto the output shaft and a radial load applied to a parallel-axis spurgear.

According to a sixth aspect, both ends of the double gear are supportedand thus a support member can stably support the double gear even if alarge falling moment is applied. This can also increase the reductionratio of the double gear.

According to a seventh aspect, the support members of the adjacentdouble gears are reinforced by a reinforcing member, e.g., a beam memberthat connects the double gears, achieving a structure with higherresistance to inclination.

According to an eighth aspect, a bearing for supporting the pinion ofthe double gear is a needle bearing, thereby reducing the diameter ofthe pinion. This can increase the reduction ratio of the double gear.

According to a ninth aspect, if a ball bearing, e.g., a deep groove ballbearing is used, the ball bearing can bear a small thrust load, forexample, a thrust load caused by weight applied to the double gear.

According to a tenth aspect, assuming that the same total reductionratio is obtained in the overall configuration, the gear wheel of one ofthe double gears has a relatively small diameter, thereby reducing thesize of a reduction-drive outer case.

According to an eleventh aspect, a shaft part extending from the endface of the double gear is supported like a cantilever by the bearing,thereby further downsizing the pinion of the double gear. Thus, areduction ratio at a point of engagement can be further increased.

The rolling friction of the oil seal may reduce the transmissionefficiency of an external force from the output shaft to an input shaft.According to a twelfth aspect, a lip is used that has a minimum tensionwithout suppressing a sealing function. This can minimize the rollingfriction, leading to a minimum friction loss. Thus, the transmissionefficiency can be further increased.

According to a thirteenth aspect, a drive motor is disposed such thatthe rotary axis of the drive motor is in parallel with the mountingsurface of an output shaft flange, thereby shortening the rotary axismodule in the direction of the output shaft.

According to a fourteenth aspect, the rotary axis module and linkmembers are combined so as to easily form articulated robots in variousforms.

The present invention was described according to the typicalembodiments. A person skilled in the art could understand that theembodiments can be changed and various other changes, omissions, andadditions may be made without departing from the scope of the presentinvention.

The invention claimed is:
 1. A rotary axis module comprising: an inputshaft connected to a drive motor; an output shaft; an output shaftflange connected to the output shaft; parallel gears coupled to theoutput shaft flange; a reduction-drive outer case rotatably supported bythe output shaft flange; a double gear train including at least twodouble gears disposed in the reduction-drive outer case; and a transfergear that transmits power of the drive motor to the double gear train,and bearings whose inner surface sides are coupled to the output shaftflange, wherein the parallel gear is engaged with a pinion of one of theat least two double gears while a gear wheel of the other double gear ofthe at least two double gears is engaged with the transfer gear, and theat least two double gears and the transfer gear are disposed in a spacebetween an inner surface of the reduction-drive outer case and theoutput shaft so as to surround the output shaft.
 2. The rotary axismodule according to claim 1, wherein the at least two double gears areeach supported by support bearings and a support member, and the supportmember is fixed to a mounting flange where the drive motor is mounted.3. The rotary axis module according to claim 2, wherein at least one ofthe support members of the double gears is supported by both of thepinion and the gear wheel.
 4. The rotary axis module according to claim1, wherein the output shaft has a hollow for passage of an umbilicalmember.
 5. The rotary axis module according to claim 1, wherein theparallel gear is an internal gear.
 6. The rotary axis module accordingto claim 1, the bearings being angular back-to-back duplex bearings. 7.The rotary axis module according to claim 1, wherein a reduction ratiobetween the parallel gear and the pinion of one of the double gears islarger than a reduction ratio between the gear wheel of one of thedouble gears and the pinion of the other double gear.
 8. The rotary axismodule according to claim 1, wherein the rotary axis module furthercomprises a mounting flange, which opposes the output shaft flange;wherein a support is mounted on the mounting flange; and wherein the atleast two double gears each include a shaft part, only one end side ofwhich is rotatably engaged with support.
 9. The rotary axis moduleaccording to claim 1, wherein an oil seal used in the rotary axis moduleincludes at least one lip that has a minimum tension without suppressinga sealing function.
 10. The rotary axis module according to claim 1,wherein the drive motor is mounted on a mounting surface of the outputshaft flange such that a rotary axis of the drive motor is in parallelwith the mounting surface.
 11. An articulated robot comprising at leastone rotary axis module according to claim
 1. 12. A rotary axis modulecomprising: an input shaft connected to a drive motor; an output shaft;an output shaft flange connected to the output shaft; parallel gearscoupled to the output shaft flange; a reduction-drive outer caserotatably supported by the output shaft flange; a double gear trainincluding at least two double gears disposed in the reduction-driveouter case; a transfer gear that transmits power of the drive motor tothe double gear train, and bearings whose inner surface sides arecoupled to the output shaft flange, wherein the parallel gear is engagedwith a pinion of one of the at least two double gears while a gear wheelof the other double gear of the at least two double gears is engagedwith the transfer gear, the at least two double gears and the transfergear are disposed in a space between an inner surface of thereduction-drive outer case and the output shaft so as to surround theoutput shaft; the at least two double gears are each supported bysupport bearings and a support member, and the support member is fixedto a mounting flange where the drive motor is mounted; and at least oneof the support members of the double gears is supported by both of thepinion and the gear wheel.
 13. The rotary axis module according to claim12, wherein the support members of the at least two double gears areconnected to each other via a reinforcing member.
 14. The rotary axismodule according to claim 12, wherein at least one of the supportbearings of the at least two double gears includes a needle bearing. 15.The rotary axis module according to claim 12, wherein at least one ofthe support bearings of the at least two double gears includes a ballbearing.